DESCRIPTION: (Applicant's Description) Treatment of early stage prostate cancer by transperineal interstitial permanent prostate brachytherapy (TIPPB) by trans-rectal ultrasound (TRUS) and fluoroscopic guidance has become an increasingly utilized option over the past decade. Post-implant computed tomography (CT) scanning for radiation dosimetry is the standard means by which to perform post-implant dosimetry (PID), which establishes TIPPB prostate coverage and implant quality. PID CT scanning is typically performed on the day of the implant or up to 4 to 6 weeks following the TIPPB procedure. Recent studies have shown that prostate radiation dose coverage may be satisfactory 80 percent to 95 percent of the time amongst experienced practitioners. Other studies have shown that prostate organ identification may vary considerably between observers and between imaging modalities. These factors serve to limit the quality of the implant and, thus, may adversely affect the PSA relapse free survival. When a suboptimal TIPPB case is identified, supplemental implantation may be undertaken. However, the optimal method to perform such supplemental implantation has not been established. This study is designed to address optimal supplemental implantation in TIPPB. The first objective of this study is to develop the procedure and technology for 'real-time' or 'during procedure' CT based PID with immediate supplemental implantation of suboptimal implants. The second objective is to develop a more accurate means than currently exists to perform PID using TRUS-CT image fusion using unique permanent interstitial multi-modality fiducials. It is anticipated that achieving these objectives will allow improved-quality image guided TIPPB using the conventional imaging technologies of TRUS, CT and fluoroscopy. It is also expected that achieving these objectives will impact on the treatment of early stage prostate cancer. Combined with the multidisciplinary expertise and commitment to collaboration of the co-investigators and the excellent environment available to them at Mayo, high confidence is held for development of an accurate and clinically useful method for real-time CT verified TIPPB.